This invention pertains to power supplies and particularly to power supplies using PWM voltage regulation to obtain a regulated output over a range of input voltages.
A conventional power supply using PWM voltage regulation contains a voltage regulator which receives a DC input voltage and produces a series of voltage pulses. These pulses are applied to a filter to obtain a regulated DC voltage at the filter output. As power supply input voltage increases, regulator input increases and the time duration of the pulses decreases in order to maintain a constant DC voltage at the filter output. If the power supply input increases sufficiently, the pulses will have such short duration that the power supply will operate inefficiently and may introduce excessive radio frequency interference into a load connected to it. The range of input voltages the supply can be used with is thereby limited.